The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure.
HAMR technology uses a laser source and a near-field transducer to heat a small spot on a magnetic disk during the recording. The heat lowers magnetic coercivity at the spot, allowing a write transducer to change the orientation of the magnetic domain at the spot. Due to the relatively high coercivity of the medium after cooling, the data is less susceptible to paramagnetic effects that lead to data errors. In general, HAMR uses laser to heat magnetic media during recording. Stability of the laser power is important for recording performance since write width, magnetic transition location, and effective write field gradient highly depends on laser power. However, laser power stability is very challenging for HAMR due to a number of factors such as space limitations, high power density, and large environmental temperature variations.